1. Field of the Invention
This invention concerns a gasoline composition having improved antiknock performance in an internal combustion engine due to the presence of certain aminofulvene derivatives.
2. Description of Related Art
The current and most inexpensive method for improving the antiknock quality of gasoline is to add one or more organometallic antiknock compounds. In the past, tetraalkyl lead compounds (more specifically tetraethyl lead) have been one of the most effective antiknock additives. However, lead compounds are being phased out because of environmental concerns related to their high toxicity. This has prompted the need to develop acceptable antiknock additives that are lead-free.
Numerous organometallic compounds possessing antiknock activity have been proposed to replace tetraethyl lead. For example, methylcyclopentadienyl manganese tricarbonyl (MMT) is known to be an effective antiknock additive (see U.S. Pat. Nos. 2,818,417; 2,839,552; and 3,127,351), and is currently used in unleaded fuels in Canada and in leaded gasoline in the U.S.
Numerous non-metallic (i.e. ashless) compounds have also been suggested as antiknock additives. Examples of such ashless compounds include 1,4 and 1,3-diaminobutanes (see U.S. Pat. No. 4,445,909), 2 -dimethylamino methyl-4-fluorophenol (see U.S. Pat. No. 4,378,231), norbornadiene (see U.S. Pat. No. 4,387,257), and alkyl carbonates (see U.S. Pat. No. 4,600,408). Particularly preferred ashless antiknock compounds are aniline and certain of its alkyl derivatives such as 2,6-dimethylaniline, n-methylaniline, n-alkyl toluidines (see U.S. Pat. No. 4,294,587), and o-aminoazides (see U.S. Pat. No. 4,266,947). However, ashless compounds have never been commercialized because of one or more debits such as high cost, relatively low antiknock quality, hydrolytic, thermal or oxidative instability, low solubility in gasoline, or high solubility in water.
Various fulvene derivatives have also been suggested as antiknock additives. For example, U.S. Pat. No. 4,264,336 discloses the use of halogenated fulvenes as antiknock compounds. However, the use of chloro or fluoro hydrocarbons an antiknock agents may be environmentally undesirable due to their detrimental effect on the ozone layer. In addition, U.S. Pat. No. 3,706,541 discloses the use of certain aminofulvenes [such as 6-dimethylamino fulvene]as antiknock additives. More recently, 6-dimethylamino fulvene has been reported to be among the most active non-metallic antiknock additives (see S. Stournos et 199th National ACS Meeting, Boston, Mass., April 22, 1990).
However, none of these patents and publications suggest that the particular class of ashless aminofulvene derivatives disclosed herein is effective in improving the antiknock performance of gasoline.